Magnetohydrodynamic stability of internal kink modes in tokamaks : application of an equilibrium code using bicubic finite elements

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TCV is a medium sized tokamak equipped with a large suite of plasma diagnostics, a versatile array of poloidal shaping coils, an electron cyclotron heating system, and a two source neutral beam injection (NBI) system. The NBI system is capable of a simultaneous injection of energetic neutrals in the co-and counter-current directions. The resulting fast ion (FI) populations are used to study a multitude of FI-driven instabilities. While plasma instabilities in the below 1 MHz frequency range can be observed

The research programme performed on the Mega Amp Spherical Tokamak (MAST) Upgrade experiment has made significant advances in developing the physics understanding of low aspect ratio tokamaks in support of the operation of ITER and design of fusion powerplants. High performance plasma scenarios have been developed to facilitate a broad programme of experiments, in which confinement is constrained by the presence of m/n = 2/1 modes that cause substantial losses of fast ions. The onset of these modes coincide

A validation of the ITER real-time reconstruction algorithms for the plasma current, centroid position, boundary and for the poloidal beta has been performed using the data collected during the first operation of the JT-60SA tokamak. The accuracy of the reconstruction is evaluated against plasma equilibria computed with the CREATE-NL nonlinear code. As it will be shown, although the setup of the magnetic sensors during JT-60SA first operation included a reduced number of sensors compared to what envisaged i

Ion temperature gradient (ITG) modes in the short wavelength regime (kθρi >1.0) known as the short wavelength ion temperature gradient (SWITG) modes, are investigated linearly and nonlinearly in the electrostatic limit for ADITYA–U tokamak, in the presence of monotonic and reversed magnetic shear using a global gyrokinetic particle–in–cell (PIC) code, ORB5. It is observed that, while the growth rate of the conventional ITG branch is reduced, the growth rate of the SWITG branch is enhanced by the reversed ma

Microturbulence can produce stationary fine-scale radial corrugations on the plasma density and temperature gradients in magnetic confinement fusion devices. We study the effect of these corrugations, focusing on electron temperature gradient (ETG) transport in the tokamak pedestal, and report three main findings. 1) In the presence of a sinusoidal background temperature gradient corrugation, each ETG mode splits into three distinct eigenvalues, with one being the original, one being more unstable and one b

The inverse equilibrium formulation and numerical code described in [L.L. Lao Phys. Fluids 24, 1431–1440 (1981)] are extended in a new `exact' fixed boundary equilibrium code that accounts for plasma toroidal rotation and pressure anisotropy. The formulation precisely captures deviations from an inverse aspect ratio

\epsilon:=a/R_0

expansion, at various orders, with

a

a minor radius and

R_0

the major radius at the magnetic axis. We show that for experimentally relevant elongation

\kappa\lesssim 2

In this work, a Model Predictive Controller (MPC) is proposed to control the plasma shape in the Tokamak à Configuration Variable (TCV). The proposed controller relies on models obtained by coupling linearized plasma response models, derived from the fge code of the Matlab EQuilibrium toolbox (MEQ) suite, with a state-space description of the core TCV magnetic control system. It optimizes the reference signals fed to this inner control loop in order to achieve the desired plasma shape while also enforcing c

A high-resolution spectroscopic system was installed on the Tokamak à Configuration Variable (TCV), whose toroidal lines-of-sight (LOS) cross the divertor region. This system simultaneously measures the Doppler broadening and Doppler shift of several spectral transitions to infer their associated ion temperatures (Ti) and the toroidal component of their flow velocities (Vi). Herein, TCV’s Tangential Divertor Spectroscopy System (TDSS) is described, along with its data analysis procedure and the first simult

The demand for megawatt-class gyrotrons for Electron Cyclotron Resonance Heating (ECRH) of nuclear fusion devices is growing significantly. It goes hand in hand with growing requirements for output power, efficiency, operating flexibility, and reliability of gyrotrons used in nuclear fusion, as well as higher demanding of the manufacturability for serial production. In Europe research and development is ongoing to fulfil that future needs, particularly, with regards to output power and efficiency. It is com

Nuclear fusion offers a promising route toward a clean and abundant energy source, though harnessing its potential remains an important scientific and engineering challenge. This thesis delves into one of the main challenges of fusion, namely managing the high heat fluxes exhausted from the plasma core. The understanding of scrape-off layer and divertor physics, which define how this heat load will be transported towards the reactor walls, is of crucial importance for the achievement of future reliable ther

Under the auspices of EUROfusion (WPMST1), the ITER baseline scenario (IBL, [1]) is jointly investigated on AUG and TCV. While the AUG results were presented at the last IAEA FEC [2], this contribution focuses on the recent results obtained in TCV and related integrated modelling results. Such developments in TCV were only possible with the installation of an NBI heating source [3], allowing ELMy H-modes at ITER relevant N. The IBL scenario is mainly characterized by low q95 (3.0-3.6), high positive triang

The scrape-off layer (SOL) sets the bounday conditions of a tokamak, determining the plasma confinement, the heat exhaust, the impurity levels, and controlling the fuelling of the device. Therefore, a first principles understanding of the physical mechanisms governing SOL turbulence is crucial on the way towards fusion energy. We describe SOL simulations carried out by using GBS, a three-dimensional numerical code that solves the drift-reduced Braginskii equations for the two-fluid model of the plasma and c

We investigate suprathermal ion dynamics in simple magnetized toroidal plasmas in the presence of electrostatic turbulence driven by the ideal interchange instability. Turbulent fields from fluid simulations are used in the nonrelativistic equation of ion motion to compute suprathermal tracer ion trajectories. Suprathermal ion dispersion starts with a brief ballistic phase, during which particles do not interact with the plasma, followed by a turbulence interaction phase. In this one simple system, we obser

Intermittent blobs, which propagate across a confining magnetic fields, are universally observed in natural and laboratory plasmas. In fusion plasmas, cross-field transport of particles and energy are associated, at least in part, with the propagation of blobs, which are therefore of great importance for the design of future fusion reactors. In TORPEX, blobs are generated from ideal interchange modes and, driven by B and curvature-induced charge separation, propagate radially outwards. An analytical blob s

This paper investigates the morphologic impacts of the widening of tributaries in confluence zones by means of systematic hydraulic tests performed in a confluent laboratory flume. The confluent channels are connected with an angle of 90° and the main channel is 0.50 m wide. The tributary is 0.15 m wide in the reference configuration and enlarged to 0.30 m over a length of 0.45 m in the widened configuration. Experiments are carried out under mobile bed conditions. Sediments with a wide grain size distribut

The unique flexibility of TCV in plasma shaping has been exploited to address different aspects of tokamak physics in which the plasma shape may play a role. This paper summarizes the experiments undertaken in the TCV tokamak ("Tokamak à Configuration Variable") over the last decade in stability and transport and offers a comprehensive and integrated view of the various effects of plasma shape observed. For each of these effects, the relation between experimental results and theoretical predictions is stres

A key issue for steady-state tokamak operation is to determine the edge conditions that are compatible both with good core confinement and with the power handling and plasma exhaust capabilities of the plasma facing components (PFCs) and divertor systems. A quantitative response to this open question will provide a robust scientific basis for reliable extrapolation of present regimes to an ITER compatible steady-state scenario. In this context, the JET programme addressing steady-state operation is focused

ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of the last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It was found that the large He content in the plasma, resulting from DC glow discharges for conditioning, leads to a confinement reduction. After the change to D glow for inter-shot conditioning, the He content quickly dropped and, in parallel, the usual H-Mode confinement with H factors clos

The effect of energetic asymmetrically distributed ions on the stability of the internal kink mode in tokamaks is analyzed. Circulating ions which intersect the resonant surface due to finite radial excursion contribute to the mode either in the region of favorable or unfavorable curvature depending on the sign of v(parallel to). Internal kink mode stabilization for predominantly cocirculating ion populations is consistent with the observation of long sawteeth using tangential coinjection of neutral beams i

A variety of techniques are being tested on ASDEX Upgrade for avoiding or reducing the divertor energy load caused by ELMs. Quiescent H-mode operation has been improved by operation with recently boronized vessel walls. Z(eff) values in QH-modes are now similar to2.5, comparable with those found in ELMy H-modes of similar density. Type It ELM operation has been generated in discharges with ICRF additional heating alone, thus demonstrating its compatibility with reactor-relevant low core momentum and particl

Magnetohydrodynamic stability of internal kink modes in tokamaks : application of an equilibrium code using bicubic finite elements

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Design, Installation, and First Results from the Ion Cyclotron Emission Diagnostic on TCV

Overview of the MAST Upgrade physics programme: testing novel concepts at low aspect ratio to inform future devices

Preliminary validation of ITER magnetic diagnostic algorithms by using JT-60SA magnetic measurements

Effect of reversed magnetic shear on short wavelength ion temperature gradient modes in ADITYA–U tokamak

Turbulence Saturation Via Fine-scale Profile Shearing in Fusion Plasmas

Investigation of finite aspect ratio effects in axisymmetric magnetic equilibria with toroidal rotation and pressure anisotropy

First Experimental Demonstration of Plasma Shape Control in a Tokamak Through Model Predictive Control

High-resolution visible spectroscopy for ion temperature and flow velocity measurements of the TCV divertor plasma

Megawatt-Class Sub-THz Gyrotrons for ECRH in Future High-Field Fusion Devices

Performance assessment of a reactor-scale tightly baffled divertor using the SOLPS-ITER software

ITER baseline scenario investigations on TCV and comparison with AUG

Plasma refuelling at the SOL simulated with the GBS code

Nondiffusive Suprathermal Ion Transport in Simple Magnetized Toroidal Plasmas

Understanding and taming plasma blobs in toroidal magnetized plasmas

Experimental study on a widening tributary channel and its influence on the confluence morphology

Physics Insight and Performance Benefit from Plasma Shaping Experiments in MHD and Energy Transport in the TCV Tokamak

Development of steady-state scenarios compatible with ITER-like wall conditions

Plasma wall interaction and its implication in an all tungsten divertor tokamak

Influence of asymmetric energetic ion distributions on sawtooth stabilization

ITER-relevant H-mode physics at ASDEX upgrade